BIOL 1441 1st Edition Lecture 4 Outline of Last Lecture I. Facts about waterII. Properties of waterOutline of Current Lecture I. Moderation of temperature (continued)II. Expansion upon freezingIII. Universal solventIV. Section 3: molecular massV. Section 4: pHCurrent LectureI. Moderation of temperature (continued)a. Evaporation- liquid to gasi. Liquid molecules all attracted to each other, molecules start moving fast enough, break all bonds, depart the liquid into the air as a gasii. Temperature- AVERAGE kinetic energy of moleculesiii. Have some molecules moving fast even at low tempiv. Heat liquid (providing energy)- average kinetic energy increasing quickerb. Heat of Vaporization: Quantity of heat a liquid must absorb for 1 g of it to be converted from the liquid to gas statei. Water has a high heat of vaporizationThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.ii. H2O needs a lot of heat to vaporizeiii. H-bonding. Must break all those bonds 1stiv. Evaporate 1 g H2O at 25 °C you need 580 cal of heatv. Heat of Vaporization significance:1. Moderate Earth’s climate2. Tropical seas absorb a large amount of solar heat3. Water evaporates- moist, warm tropical air4. Warm air circulates poleward- releasing heat5. Lose heat, forming more H-bonds6. Gas- liquid- RAIN!vi. Surface water that is evaporating- highest kinetic energy- “hottest”c. Evaporative Cooling- avg temperature dropsi. Contributes to the stability of temp in lakes and pondsii. Prevents terrestrials from overheatingiii. Water evaporates from plant leaves, prevents tissue from becoming too warm in suniv. Sweat cools you off- evaporates off of your skin, dissipating your body heat1. High humidity is hotter, why?- because already so much water in the air cant come off of your skinII. Expansion Upon Freezinga. Water is less dense as a solid (ice) than a liquidb. Solids have more molecules packed tightly togetherc. More mass- heavyd. So why is water lighter as a solid? i. Water expands instead of contracting below 4 °C ii. H-bonding!!! e. Behaves like other liquids when at 4 °C or abovef. Expands as it warmsg. Contracts as it cools i. Below 4 °C behaves very uniquely1. Starts expanding! 2. Water is densest at 4 °C ii. Freezing- molecules are no longer moving vigorously enough to break H-bonds1. 0 °C water locks into a crystal lattice- each molecule bonds to 4 partners2. H-bond -set distance apart3. Ice 10% less dense than liquid 4. water at 4 °C(10% fewer molecules for same volume) 5. If ice sank, life as we know it would cease to exista. All ponds, lakes and oceans would freeze solidb. Summer thaw only the upper few inches of the oceanc. All the animals burrowed into sediments dieIII. Universal Solventa. Solution- liquid that is completely homogeneous mixture of 2 or more substancesi. salt water, salt dissolves and the concentration is then uniform throughout the waterb. Solvent- dissolving agent (water)c. Solute- substance that is dissolved (salt)d. Aqueous solution- water is solventi. NaCl- ionic compound (Na+ cation, Cl- anion)ii. Surface of salt crystal – charges iii. Attracted to water- chargeiv. Oxygen (-) attracted to Na+v. Hydrogen (+) attracted to Cl-vi. Water molecule surrounds 1. individual Na+ or Cl- ionse. Sphere of water moleculesi. Hydration Shellii. Separates them, shields them from one anotherf. Compound does not need to be ionic to be dissolvedi. Nonionic polar molecules- sugar moleculesii. Ionic compound- each individual atom has a chargeiii. Nonionic compound- atoms have no chargeiv. Polar molecule- charge difference throughout the moleculeg. Hydrophilic & Hydrophobic Substancesi. Hydro- water Phiolios- lovingii. Hydro- water Phobos- fearingiii. Hydrophilic- any substance with attraction to water (charges)1. Ionic or polar substances2. Dissolve in water3. Some large molecules inside of cells do not dissolve- remain suspended in liquid portion of the cella. Colloid- stable suspension of fine particles in a liquidi. EX. Cotton1. Cellulose- very large molecules with regionsof partial +/- charges2. Water will adhere to cellulose3. Cotton will absorb water well4. Cotton towels & t-shirts- good dryingiv. Hydrophobic1. Nonionic & nonpolar substances repel water2. Olive oil- nonpolar bonds (no charge- share electrons equally)3. Cell membranes- hydrophobicv. Like Dissolves Like1. Charged molecules attracted to charged moleculesa. Hydrophilic moleculesi. Ionic substancesii. Polar molecules- polar covalent bond2. Uncharged molecules attracted to uncharged moleculesa. Hydrophobic moleculesi. Nonpolar molecules- nonpolar bondsii. NO chargeIV. Section 3: Molecular Mass a. Almost every chemical rxn in your body occurs in H2Ob. To understand these rxn’s, we must know how many atoms & molecules are involvedi. How many molecules are in this solution?ii. Use mass to determine number of moleculesc. Molecular Massi. We know the mass of each atom in a given moleculeii. Mass of atom = # protons + # neutrons (atomic mass)d. Molecular mass- sum of the masses of all the atoms’ in a moleculei. H2O: 2 hydrogen atoms & 1 oxygen atom 1. H2O – molecular formulaii. Sucrose (table sugar)1. Molecular formula: C12H22O11iii. Determine mass each atom1. C = 12 daltons2. H = 1 dalton3. O = 16 daltonsiv. Mass x number of atoms in molecule1. Carbon = 12 dal x 12 atoms = 144 dal2. Hydrogen = 1 dal x 22 atoms = 22 dal3. Oxygen = 16 dal x 11 atoms = 176 dal4. 1 molecule of sucrose = 342 daltonsv. Moles1. 342 daltons- can’t weigh that out!2. Use conversion: Avogadro’s numbera. Mole (mol) = 6.02 x 1023 molecules b. 6.02 x 1023 daltons in 1 gramc. 1 mol sucrose = 342 g MOLAR MASSd. 6.02 x 1023 sucrose molecules = 342 g = 1 mole. 1 mol = 6.02 x 1023 molecules ® Quantityf. 6.02 x 1023 daltons = 1 gram ® Weightg. 6.02 x 10 23 molecules x 342 daltons x 1 g = 342 gramsh. 1 molecule 6.02 x 1023 daltons i. 1 sucrose molecule = 342 daltonsj. 6.02 x 1023 molecules x 342 daltons = 2.06 x 1026 daltons 3. 2.06 x 1026 daltons x 1 g = 342 g4. 6.02 x 1023 daltons5. 1 mol = molecular mass (g)6. 1 mol of any substance = molecular mass (g)7. Need 1 mol of water, how much do you weigh out?a. What is the molecular mass of water? 18 daltonsb. Answer: 18 g water = 1 moli. Water: 1 mol =18 gii. Sucrose: 1 mol = 342 giii. Ethyl alcohol: 1 mol = 46 gvi. Molarity1. Molarity- number of moles